The Horsehead Nebula is a cloud of ionized-hydrogen in the constellation Orion. These clouds are lit from within by young, hot stars. The interstellar dust absorbs the light from part of the ionized cloud creating this beautiful contrast. Image Credit: NASA, NOAO, ESA and The Hubble Heritage Team (STScI/AURA)

Top 10 Mysterious World Landmarks

Not far from the famous Inca city of Machu Picchu lies Sacsayhuaman, a strange embankment of stone walls located just outside of Cuzco. The series of three walls was assembled from massive 200-ton blocks of rock and limestone, and they are arranged in a zigzag pattern along the hillside. The longest is roughly 1000 feet in length and each stands some fifteen feet tall. The monument is in astonishingly good condition for its age, especially considering the region’s propensity for earthquakes.